To evaluate the prognostic value of the S-phase fraction (SPF) and the correlation with other clinicopathologic factors in node negative breast cancer.

From 1995 to 1998, seventy one breast carcinoma tumors with T1-2NOMO staging were prospectively sampled as fresh tumors for flow cytometric DNA analysis. We determined the nuclear DNA content, and the SPF was calculated from DNA histograms. We evaluated the relationship between the SPF and other clinicopathologic factors (age, tumor size, tumor grade and, steroid receptor status). The five year distant relapse free survival (DRFS) and overall survival (OS), according to the SPF, were determined.

The SPF ranged from 0.1 to 50.9% (median: 13.4%). The SPF was dichotomized using the median value to divide patients into 38 patients (53.5%) having tumors with the low SPF and 33 patients (46.5%) having tumors with the high SPF. The patient's age and the tumor size were not significantly associated with the SPF. High SPF was associated with high tumor grade, but this did not reach statistical significance. There was a significant correlation between high SPF and estrogen receptor negativity; 34.4% of ER positive tumor had high SPF, whereas 58.3% of ER negative tumor had high SPF(p = 0.042). The mean follow up duration was 65.0 months (median: 62.3). Among 71 patients, there were 4 (5.6%) cases of local recurrence, 7 (9.9%) cases of systemic recurrence and 10 (14.1%) cases of disease related death. The patients with high SPF showed a poorer 5 years DRFS and as than did the patients with low SPF (87.9% vs. 91.2%; 80.4% vs. 94.5%, respectively), but the difference had no statistical significance.

The present data was insufficient to use SPF information for the selection of the type of adjuvant therapy, but SPF is a promising prognostic factor for node negative breast cancer. Further study with a sufficient number of patients is needed and this should lead to a better understanding of SPF in node negative breast cancer.